Filter
Top Products
STAAD Commands and Input Instructions
Section 5
5-332
In this example, the Rayleigh frequency for load case 1 will be
calculated. The output will produce the value of the frequency in
cycles per second (cps), the maximum deflection along with the
global direction and the joint number where it occurs.
Since the AREA LOAD is in the global Y direction, the displaced
shape to be used as the mode will be in the Y direction. If you
want a mode or frequency to be for lateral motion (X or Z), then
enter the loads in the X or Z directions. Entering loads in the
vertical direction when the first mode is in the lateral direction is a
common mistake.
Notes
This command is based on the Rayleigh method of iteration using
1 iteration. The frequency calculated estimates the frequency as if
the structure were constrained to vibrate in the static deflected
shape generated by the loads in the load case.
In many instances, the forces should be in one global direction to
get the mode and frequency associated with that direction.